1. Field of the Invention
The present invention relates to a thermopile-type thermoelectric sensor in which a plurality of patterns constituting thermocouples hereinafter, each of patterns is called a thermoelectric patterns are connected in series, the middle portion constitutes a light receiving portion hot junction portions of the thermoelectric patterns are disposed in the light receiving portion, and each of the thermoelectric patterns is radially disposed.
2. Description of the Related Art
In thermopile-type thermoelectric sensors, because many thermoelectric patterns are connected in series so as to obtain high sensitivity characteristics, it is required to reduce their output variations, and, therefore, up to now, various improvements have been carried out. For example, in a thermopile-type thermoelectric sensor shown in Japanese Unexamined Patent application Publication No. 10-19666, the thermal resistance of a thermoelectric pattern in the vicinity of the end of a membrane is set to be smaller than the thermal resistance near the not junction, and in this way, the temperature gradient of the thermoelectric pattern in the end portion of the membrane is reduced, and even if the dimension of the membrane is varied, the affect on output variations is made to be reduced.
However, in the above construction, output variations caused by dimensional variation of the membrane can be reduced, but there was a problem that the membrane was not effective against other variations such as dimensional variation of the thermoelectric pattern, dimensional variation and variation of the absorption factor of an infrared absorber to be disposed in the light receiving portion, etc.
Accordingly, it is an object of the present invention to provide a thermopile-type thermoelectric sensor for fulfilling adjustment functions of output variations, which is effective against all variations caused by the structure of the thermopile-type thermoelectric sensor.
A thermopile-type thermoelectric sensor according to the present invention is constructed so that the sensor may solve the above-mentioned problem as in the following.
(1) FIG. 1 is a top view when one example of a thermopile-type thermoelectric sensor according to the present invention is looked at from above. A pair of patterns (a thermoelectric pattern) is composed of a first pattern of thermoelectric material and a second pattern of thermoelectric material, and a thermoelectric pattern 1 is formed by connecting a plurality of these thermoelectric patterns in series. In the thermoelectric pattern is the thermoelectric patterns are radially arranged so that the hot junction of each thermoelectric pattern may be disposed in the middle portion of the sensor, a light receiving portion 2 is formed in this middle portion, and a thermoelectromotive force is generated in the thermoelectric pattern 1 by increasing the temperature of the light receiving portion 2 through an infrared absorber, etc., not shown in the drawing. In the present invention, a thermoelectric pattern 3 for sensitivity adjustment is connected to the thermoelectric pattern 1 in series. In this thermoelectric pattern 3 for sensitivity adjustment, short-circuited patterns for short-circuiting patterns are provided, and by cutting off these short-circuited patterns selectively by laser, etc., the output of the thermoelectric pattern 1 can be adjusted. The thermoelectric pattern 3 for sensitivity adjustment is formed at the same time when the thermoelectric pattern 1 is formed, and accordingly no burden increases in the manufacturing processes.
(2) In the present invention, instead of the short-circuited patterns provided in the thermoelectric pattern 3 for sensitivity adjustment, it is possible to lead out at least one lead-out pattern from patterns. By making the lead-out patterns short-circuited or open properly in a selective way, the output of the thermoelectric pattern 1 can be adjusted.
In a thermopile-type thermoelectric sensor according to the present invention, the above-mentioned first construction (1) or second construction (2) is mainly adopted, but in the first construction (1) the short-circuited patterns can be constructed in the following way.
Firstly, the short-circuited patterns can be constructed so as to short-circuit cold junctions themselves. Furthermore, a plurality of short-circuited patterns to be disposed between hot junctions and cold junctions can be formed. In the latter construction, fine adjustment of the output can be achieved.
Furthermore, in the above-mentioned first construction (1) and second construction (2), the polarity of thermoelectromotive forces in thermoelectric patterns for sensitivity adjustment can be decided as in the following way.
First, a thermoelectric pattern for sensitivity adjustment can be formed so as to generate a thermoelectromotive force of same polarity as a thermoelectric pattern. In this case, in the above-mentioned first construction (1), as the short-circuited patterns are cut off, the output of the thermoelectric sensor increased. Furthermore, in the second construction (2), as the lead-out patterns are short-circuited, the output of the thermoelectric sensor decreases.
Moreover, the thermoelectric pattern for sensitivity adjustment can be formed so as to generate a thermoelectromotive force of opposite polarity to the thermoelectric pattern. In this case, in the above-mentioned first construction (1) as the short-circuited patterns are not off, the output of the thermoelectric pattern decreases. Furthermore, in the above-mentioned second construction (2), as the lead-out patterns are short-circuited, the output of the thermoelectric pattern increases.
Furthermore, a combination of a thermoelectric pattern for sensitivity adjustment formed so as to generate a thermoelectromotive force of opposite polarity to the thermoelectric pattern can be also constructed.